1. Field of the Invention
The present invention relates to a scanning exposure apparatus of a projection type, which performs projection exposure of an original pattern on a photomask onto a photosensitive substrate while moving both the photomask and the photosensitive substrate at a time.
2. Related Background Art
In fabricating semiconductor devices, liquid crystal display devices or thin-film magnetic heads by the photolithography technology, projection exposure apparatus have been used to perform exposure of an original pattern on a photomask or reticle onto a substrate such as a wafer or a glass plate coated for example with a photoresist through a projection optical system. Recently, a chip pattern for semiconductor devices tends to increase its size and therefore the projection exposure apparatus are required to increase the exposure area to transfer a larger area on the reticle onto the photosensitive substrate.
Then, there are developed projection exposure apparatus of a so-called slit scan exposure method, which successively transfer segments of a pattern on a reticle onto a substrate while moving the reticle and the photosensitive substrate in synchronization, forming an illumination area for example of a rectangle, an arc or a hexagon (as will be referred to as "slit illumination area"). Such projection exposure apparatus are provided with an alignment apparatus for performing positioning (alignment) between each shot area and the reticle from a positional relation between an alignment mark (wafer mark) for each shot area on the substrate and an alignment mark (reticle mark) on the reticle (Japanese Laid-open Patent Application No. 4-307720).
Also, U.S. Pat. No. 4,301,363 discloses such a technology that alignment light is scanned to the alignment mark using a polygon mirror.